Merge topic 'print-sources'

d8dcfa7776 Tests: Add tests for CMakePrintHelpers
b7ddfcfe08 cmake_print_properties(): Update grammar docs
e52b9e1270 PrintHelpers: Document argument order restriction
d87ed4d88f PrintHelpers: Fix indentation
5fa70e1738 PrintHelpers: Rewrite a few more error messages
2579503f45 PrintHelpers: Fix target SOURCES property

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !7331